A breath of fresh air in the fight against drink drivers

The interlocks – portable breathalyser units that require a driver to blow into it before a car will start – will be demonstrated today at the Royal Australasian College of Surgeons by the device's manufacturer for Transport Minister Peter Bat

A breath of fresh air in the fight against drink drivers

The new laws provide that motorists can be jailed for up to four months and their cars clamped for 12 months for avoiding, circumventing or disconnecting interlocks.

Guardian Interlock Systems Australasia, which supplies units to the South Australian Government's interlock program, said units could distinguish a human breath from other stored sources of air.

Drivers had tried unsuccessfully to substitute compressed air, inflated balloons and even bagpipes for breath samples, said the company's managing director, Les Libbesson.

Drivers have to blow into the device for at least eight seconds, to expel breath from the depths of the lungs, then introduce a four-second "hum tone".

The hum tone allows the machine to confirm that the sample came from a person.

The breath sample is too large for most children's lungs at the pressure required.

Lock-out periods, when the car will not start, apply if alcohol is detected. If no alcohol is detected, the car will start, but drivers have to periodically provide repeat breath samples on their journey to ensure their continued alcohol-free status.

The interlock's dash-mounted control unit indicates when a repeat sample is required, and offers a "period of grace" of a few minutes for a driver to pull over and blow into the unit again.

If samples fail the test, the car's lights will flash and horn will sound until the engine is turned off.

Mr Libbesson said that while a car was being driven, the units never cut the engine. But the lights and horn alarms would bring unwanted attention to the driver.

The units will cost motorists about $100 to $120 a month for fitting and servicing.